Separation of eutectic-forming mixtures by crystallization



ATIoN D. L. MCKAY May 25, 1954 SEPARATION OF EUTECTIC-FORMING MIXTURES BY CRYSTALLIZ Filed Dec. 22, 1949 lkml!! mmsmmmzu uzbFSm mm mm IN VEN TOR.

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Patented May 25, 1954 SEPARATION F MIXTURES BY Phillips Delaware EUTECTIC-FORMING CRYSTALLIZATION Dwight L. McKay, Bartlesville,

Petroleum Company, a corporation of Okla., assignor to Application December 22, 1949, Serial No. 134,390 4 claims. (ci. 26o-674) This invention relates to a continuous process and apparatus for separating binary mixtures, the components of which are completely miscible in the liquid state and completely immiscible in In one aspect, it relates to a process and apparatus for separating binary eutectic-forming mixtures oi organi-c compounds.

In separating binary mixtures by crystallization, when each of the components becomes completely saturated. with respect to the other, further abstraction of heat will crystallize both components as a heterogeneous mass and in a definite ratio of concentrations. This is commonly referred to as a eutectic mixture. In a eutectic mixture, the components are completely miscible when in the liquid state and completely immiscible when in the solid state. In contrast, in a solid solution-forming mixture, the components are at least partially miscible with each other in the solid state.

Ii one of the components of a eutectic-forming mixture is present in excess of the concentration dened by the eutectic composition, that component is the saturating component and the other is the saturated component. When a eutectic-iorming liquid mixture in which one of the components is present in excess of that defined by the eutectic composition is cooled, the mixture becomes saturated first with the saturating component and the amount of the saturating component in excess of that deiined by the eutectic composition can be crystallized and removed to leave a mixture having the eutectic composition. No further separation is possible by ordinary crystallization methods. The prior art discloses processes for separating a iew specific mixtures by the addition of a third component to a binary eutectic mixture to produce a ternary mixture in which one of the original two components is present in excess of the ternary eutectic composition.

In referring to mixtures having the eutectic composition, it is to be understood that mixtures of near-eutectic composition are included. As a practical matter, it is hardly likely that a mix'- ture of the exact eutectic composition would ever be obtained in a large scale crystallization operation. i-lovi ever, for my purpose, when as much as practical lof the saturating component has been crystallized vithout danger oi crystallization of eutectic mixture, the remaining mixture is referred to as having the eutectic composition.

The temperature at which a solid phase having the eutectic composition crystallizes is a definite and xed temperature at a given pressure.

and this temperature is perature.

I have invented a process and apparatus for effecting the continuous separation of binary eutectic mixtures into their components. According to my process, when the excess of a saturating component has been crystallized and removed leaving a liquid mixture having a eutectic composition, I contact the eutectic liquid with a solid adsorbent material which preferentially adsorbs one of the components. This operation leaves a residual liquid rich in the other component, and the other component then is the saturating coinponent. From this residual liquid some of the other component may be recovered by crystallization. The adsorbed material recovered from the adsorbent is termed desorbate, and in this case the desorbate recovered from the adsorbent is rich in that component which is preferentially adsorbed, and this component then becomes the saturating component in the desorbate and it may be separated by crystallization.

By using my process and apparatus, which will hereinafter be described, I am able to introduce a feed of eutectic-forming material continuously into the apparatus and remove from opposite ends the components in substantially pure form. My invention will be more clearly understood upon reading the following detailed description, drawing, and claims.

In the drawing, Figure 1 is a schematic diagram of my apparatus showing the different zones and points of addition and withdrawal for making separations according to my new process.

Figure 2 is a solid-liquid phase diagram for a two-component system.

Figure 3 is a curve representative of the type of adsorption isotherm obtained where one component is selectively adsorbed over part of the concentration range and another component is selectively adsorbed over the remainder of the concentration range.

Figure 4 is illustrative of the type of adsorption isotherm where one component is selectively adsorbed throughout the entire concentration range.

In Figure 1 oi the drawing, the apparatus consists of an elongated cylindrical tube l l which is horizontally disposed. 'Ihe ends of this tube are closed except for openings for attachment of a pipe lli at one end, and of pipe 32 and conduit 3l at the other end. Disposed in this tube Il is aI conveyor I t which I have shown diagrammatically as a screw conveyor. The shaft of this screw conveyor I8 also extends through the end called the eutectic temwall I2 of the tube. rlhis conveyor is rotated by the source of power I9. In the opposite end of the tube H is a conveyor 36, also illustrated as a screw conveyor. The shaft of this conveyor er.- tends through the end wall i3 to a source of power 31. Pipes E2, 64, 5t, 52, 55, and 16 are connected to the tube H in the generally central portion of the tube H as illustrated in the ligure. The inner end of the screw conveyor I8 does not quite reach the midpoint of the tube, while the inner end of the conveyor extends'a short distance to the left of the midpoint of the tube. Surrounding the mid-section of the tbe H is a heater element 4l while a heater 'i5 isV disposed at a point near the left end of the tube and a heater 53 at a point near the right hand end of the tube. Sufcient distance should be lleft between the ends of the heating elements l5 and 33 and the respective tube ends so 'that end plates I2 and i3 may be bolted or otherwise attached to the ends of the tube. Also, suiicient space should be allowed for making pipe connections in case'such are desired at these points. `Some pipes i6 and i1 are for inlet and outlet of a heating agent to heater I5. Pipes 34 and 35 are for inlet and outlet of the heating agent to heater 33. Pipes d2 and 43 are likewise for in- 'let and outlet of a heating agent to heater 4l.

Between heaters 4l and i5, but relatively close `to heater 4I, is disposed a cooler 44. The cooler 44 may, if desired, actually touch the heater (il, but it is preferable to have these heat exchange lelements sulciently separated that heat will not exchange between them.

44. A cooler 41 isdisposed between heating element 4| and heater 33, but relatively closer to 'heater 4I. This cooler l1 should likewise preferably be spaced a short distance from the heater 4|. Pipes 48 and 49 are for inlet and outlet of l inner end of pipe to prevent withdrawal of solid i material from the tube H. A pump 5| is provided in pipe 50 for transfer of liquid. The outer end of pipe 59 is manifolded to pipes 5?. and 54 as shown. Pipes 52 and 54 are provided with valves 53 and 55, respectively. An opening 82 in separator plate 8l makes provision that liquid Yflowing from the region of the cooler 44 to the heater 4| is introduced into this latter zone at a point near the point of addition of a solid adsorbent material. tached to the tube l l in about the positions illus trated in the drawing. Pipe E4 is connected to a pipe S3 and a pipe 10 which pipes carry valves 55 and 69, respectively. Beyond valve 69, pipe 1B .connects to pipes 62 and 53, the former of which is provided with a valve E6. A pipe @l carrying a valve Sil is attached to pipe 82 and upstream of the valve El), pipe 5i is attached to pipe G3 which, as mentioned above, is provided with valve 65. Unit 61 is an adsorbent regenerator unit. It may be termed a desorption unit. From unit 5'! a conduit 1l leads to the conduit 12. To these ytwo conduits is connected a conduit 13. Since the desorption unit G1 will treat a solid adsorbent material, the conduits 3l, 1 I 12, and 13 will need to be of a type. to transfer solid adsorbent material. For example, these conduits may be screw conveyors, piston type conveyors, or even bucket conveyors, or any other type of conveyor adapted Pipes 45 and 45 are 'for inlet and outlet of a cooling agent for cooler Pipes S2 and 64 are at- .fr

to the transfer of solid adsorbent material under conditions of operation to be described herein.

The heaters I5, 33, and 4l may be of any type of heater desired, while the coolers 44 and 41 may lilrewise be any type of cooler desired, provided, of course, such are adaptable for the heating and cooling problems of `my invention.

The section of the tube i i between the cooler 44 and the heater i5 should preferably be insulated with some type of encient insulating material. The section oi' the tube H between the cooler 41 and the heater 33 should also be provided with insulation 'i These two sections of tube H should be insulated since it is desired that heat in these sections should not be lost to, or received from, the atmosphere.

Figure 2 is a diagrammatic representation o a solid-liquid phase diagram for a two-component eutectic-forming system. For illustrative purposes, I will term the components A and B. The point at Awhich the lefthand curve of Figure 2 touches the lefthand'ordinate represents the melting point oi the component B, while the point at which the righthand curve touches the righthand ordinate represents the melting point of the i component A. The leithand curve of this figure is a curve showing the depression of the melting point of component B as caused by the presence of component A. When component B becomes saturated with component A, the melting point is represented by the lowest point of this curve. In like manner, the righthand curve is actually a melting point curve of component A containing various concentrations of component B, vand the lower end of this curve, which is coincident with the lower end o1" the other curve, represents the melting point of A when it is saturated with corn- Aponent B. The lower end of these two curves is actually the temperature representing the melting point of A saturated with B, and B saturated with A, which temperature is the eutectic temperature. The concentration of the system under -these conditions is the eutectic concentration or composition. Under a given pressure condition, the eutectic point of such a system represents a non-variant point, and the temperature and concentration are fixed.

A broken line X is drawn through the eutectic point horizontally until it intersects the ordinates representing per cent B and 100 per cent A. The melting point curve of component B is iden- .tif-led by reference letter Y and the melting point curve of component A is represented by reference :letter Z. The area above the curves Y and Z represent liquid conditions. The area under the -curve Z and above the line X represents a twophase region in which solid component A is in equilibrium with solution. The area under the curve Y also represents a two-phase region in which solid component B is in equilibrium with liquid. At all temperatures below the line X, the entire system is a solid and this solid may be all eutectic or part component A and eutectic, or it may be part component B and eutectic.

In the apparatus illustrated in Figure l, a binary system consisting of components A and B, the phase diagram of which is illustrated in Figure 2, is separated into these components.

Assuming for purposes of illustration that the feed stock is a mixture of 50 per cent A and 50 per cent B, this feed stock in a liquid state is introduced into the system through line 5l from a source, not shown. The feed passes through valve 6G and line 52 into the tube crystallizer H. The liquid upon entering the tube at rst hows in both directions from its point of inlet. The liquid which lovvs toward'the left in the tube reaches the region of the cooler il and since this charge stock contains compocooler, will be cooled to a temperature nearly as low as the eutectic temperature indicated in the diagram of Figure 2. Under these conditions a substantial quantity of component A will be frozen out from the solution. The conveyor 3S is operated in such a manner that solid material is moved from a midpoint longitudinally of the tube H toward the endl I3. The solid component A frozen out in coo." er 47 will then be moved from left to right by the conveyor 36. This solid material continues to move toward the right until it reaches the region of the heater 33. This heater is intended to be operated at a temperature above the melting point of component A so that the solid phase of component A will be melted. The liquid contents of the tube il to the right of the heater 33 is intended to be pure liquid component A, and this material A is removed as product through the line 32 in the liquid state.

As mentioned above, the degree of cooling carried out in cooler lll is intended to freeze out all or substantially all of component A in excess the tube l i. This adsorbent material is so selected that it will preferentially adsorb component A to a greater extent than it will adsorb component B under conditions existing in the central portion of the tube Il. By the term sorbing A and B in a ratio greater than the eutectic ratio 15/85. When an adsorbent adsorbs more than l5 per cent A and less than 85 ponent A and accordingly is enriched in component B. This solution then contains B as the saturating component and some B may be recomponent A with some component B then is moved by the conveyor 35 in the direction of the heater 33. vBy the time the solid adsorbent with Aits charge of adsorbed A and occluded B reaches -sulation '14.

'the region of the cooler 41, it is joined by the crystallized component A which froze out in the chiller 41. This mixture of solids then is slowly moved by conveyor 36 from the region of cooler 41 toward the heater 33. Since solid material which, of course, Will occupy the lower portion of the tube 36, is transferred from left to right, it will be displaced by liquid movingJr from right to left in the tube. Since the solid material in the tube during transfer is continuously agitated, liquid nov/ing from right to left will, of course, contact this solid material and a general refiuxing operation occurs. In the region of the heater 33, liquid A is present in a relatively pure condition and some of this liquid is the liquid which ovvs from the right toward the left in the tube Il. This liquid A tends to Wash the correspondingly.

In addition to selecting an adsorbent which will adsorb component A preferentially over regeneration unit S7. .Substantially pure liquid component A is removed from the tube through the line 32 to such disposal as desired.

The changes occurring Within the contents of gain of heat from the atmosphere bythe in- Due to the general reluxing operation taking place in this section y5l, there is a progressive increase in the concentration of component A and in temperature from left to right.

After the solid adsorbent material has adsorbed some co ponent A from the eutectic liqtion of the remaining liquid is altered and it is no longer a eutectic mixture. This liquid is then richer in component B, andV component B becomes the saturating component. This component B will not' freeze out simultaneously.

'Since the reaminingT liquid in the region of the heater 4l contains component B as the saturatliquid in cooler 44, the

`41. within the tube i I '7 ing component', this liquid is then withdrawn from'A the tube II through the pipe 50 and is transferred under the influence of the pump I through pipe 52 and valve 53 to apoint in the adiabatic section 58`of the tube I'I near the cooler 44'.y This section 58= is an adiabatic section similar tosection 5i at the other end of the tube. Section 58 is insulated by insulation 15- against transfer of heat to or from the atmosphere. The liquid entering section 58 through pipe 52 flows into the cooler 44 and this cooler is operated at such a temperature that some component B will crystallize out as= a solid. This temperature is also maintained at a value at least slightly above the eutectic temperature so that solid eutectic will not form atv this point. When solid B separates from? the solution' in cooler 44, the conveyor I8 operates to move the solid component B from the reg-ion of the cooler 44 toward the heater I5. Solid. component B ponent A. This heater l5 is, of course, operated at' such a temperature as will' melt component B and some B willflow toward theV cooler 44.

There is accordingly, a refluxing at thispoint and a progressivel increase in the concentration of component B` on passing from right to left in the adiabatic section 58. Pure liquid component B is removed from the system through the pipe t4'f for such disposal as desired.

The solidf adsorbent material with its adsorbed component B= and some occluded component A which is removed from the tube I I through conduit- 3I, passed to an adsorbent regeneration system. This adsorbent regeneration system may be any desired, provided it serves to remove the occluded and adsorbed components from the adsorbent in a satisfactory manner. The regeneration operation may include a heating step and stripping with steam or an inert gas', as desired, provided, of course, none of the stripping agents are detri mental to'the adsorption efficiency of the adsorbent. The adsorbent freed' of its charge of components isI passed from the regeneration apparatus 61 through thevconveyor 1I` and conveyor 12 andv is recycled to the adsorption zone. Makeup adsorbent material may be introduced into the systm through the conduit or conveyor 13 from a source not shown and as needed.

When solid component B is frozen from the component B is transferred by the conveyor in the direction of the heater' I5. The liquid remaining' in the cooler 44 is substantiallyof a eutectic composition provided the coolerv temperature at, or very near, the eutectic temperature. This cooler should not cool the liquid to a temperature below the eutectic temperature since under such a condition solid eutectic would form in the cooler and the formation of solid eutectic is to be avoided. The residual eutectic' liquid from the cooler Gli works its way from the region of' this cooler into the end of the heater 4I in which it is mixed with the liquid of eutectic composition originating in the cooler 41, and it is this mixture of eutectic liquids originatingv from both of the coolers which is contacted by the solid adsorbent in the region of the heater The screen 56 or other means is provided `to prevent solid adsorbent material from passing into and through line 50 and line 52, along with liquid into the B component recovery end of the tube II.

The recoveredA components A and B from the adsorbent regeneration apparatus 51 are passed carries some occluded cornsystem has chilled its contents' to a through they conduit 682 andi throughzvalvg B6 to be combined with'. the feed stock: introduced through line 62 case this desorbate material has a compositionnear that-of the original feed stock. In case the composition of the desorbate flowing through line- 68 is nearer the composition of liquidl being transferred through pipes 50 and 52 by pump 5I into the B recovery end of the unit, this desorbate material will then be passed through valve 69 and line 1IlI into the B recovery end of the crystallizer. Valve 66` will, of course, be closed. When desorbate is added to the feed in line 62, valve B61 isopen and valve 69 will be closed.

In oase the original feed stock composed of components A and B contains component Blas the saturating component, valve 60 will be closed andthe feed streamwillbe passed through valve 65 and lines 63 and 64 into'the B recovery end of the crystallizer.. When B is the saturating component and the feed-is introduced through line 64', the operation ofthe remainder of the system is exactly like that described' hereinbefore for the system when component A is thel saturating component and the feed stock is introduced through line 62.

Under the conditions that component A is-the saturating component of the feed stock and the feed isintroduced through line 62 and the adsorbent materialV is of suchV a type that component B is adsorbed fromthe eutectic liquid in the region of heater 4^I, the liquid remaining in heater 4I again contains: component A as the saturating` component and'. this liquid is then transferred througha. pipe 50- and pipe` 54 under the influence of pump 5I- into the component A recovery end ofA the crystallizer. Under these latter conditions, the solid adsorbent material will need to be passed through the system in relatively largefquantities and large amounts of component B will be adsorbed and carried intothe adsorbent regeneration' sytsem 6.1 Descr-bate from the regenerator B1 will` then be rich in component Band this descr-bate will then pass through line 68, valve 69, and lines 10 and 64 intoA the B- recovery end of the crystallizer. Component B will be frozen out in cooler 44 and solid B transferred toward heater I5 with refluxing as. described above. Pure component B willbe removed through line I-4. Hquidzeutectic remaining as a residue in cooler 44 willthen Workv its way by passing through opening 82A in partition plate 8l intol the region of the' heater 4I.` in which it will combine` with the eutectic liquid from cooler 41- to be contacted by the adsorbent.

Under the condition when-component B is the saturating` component and component B i's the component. adsorbedby the' adsorbent, the feed stock will be introduced into the system through the linev 64. Component B will. be crystallized in cooler 44 and solid -B will thenbe moved to the heater I5 as-described.above. Theeuteotioliquid remaining in cooler 44 works itsV way through the opening 82 in plate 8|` into the region of the heater 4I to be contacted with the absorbent. The adsorbent removes by adsorptionv some of component B so that the liquidi remaining in the region of the heater 4-I- contains component A as a saturating compone -t. This remaining liquid A is removed from this regionthrough' pipes 50 and 54 and is` added to the. A recovery end of the crystallizer. The' liquidA entering the tube II- from pipe 54 werkeI its-way into the cooler: 41 inwhich some solid component A crystasllizes,

y remaining from the adsorption and this component is then moved in the direction of the heater 33. Component A as a liquid is removed through pipe 32, while the solid adsorbent With its adsorbed component B and some occluded component A is transferred by conveyor 3| to the regeneration unit 6l. Under these conditions desorbate from the regeneration apparatus is rich in component B, and it is passed through line 68, valve 69, and lines 'i0 and 64 into the B end of the crystallizer.

Under the conditions when the feed stock is composed of a mixture of components A and B of eutectic composition, the charge may be introduced from the feed line 63 through line 59, line 83, valve 84, and pipe 'I2 along with the adsorbent into the crystallizer tube. This liquid feed stock may, of course, be passed into the crystallizer apparatus through a separate tube I6 at about the adsorbent feed point, if desired. The feed stock eutectic mixture is added to the system at a point near the adsorbent addition point so that the adsorbent will have an opportunity to adsorb one of the components preferentially to the other to break the eutectic so that the cooler 54 or the cooler lil may be able to crystallize the excess of component B or component A from the liquid remaining after adsorption. In this latter case, if component A is adsorbed from the eutectic feed stock, the liquid contains component B as a saturating component and this residual liquid is transferred through pipes and 52 into the B end of the crystallizer. In case component B is the component adsorbed by the adsorbent from the eutectic mixture feedstock, the liquid remaining from the adsorption contains component A as the saturating component and this residual liquid is then transferred through pipes 50 and 54 into the A component end of the crystallizer. The operation in other respects is exactly the same as hereinbefore described.

The adiabatic sections of my crystallizer apparatus 51 and 58 are intended to be well-insulated so that the reuxing action within these sections will be as nearly complete as possible.

Specific example As an example of the utility of my apparatus for separating a two-component eutectic forming system into its components, I will describe the separation of benzene from normal heptane. Benzene possesses a melting point of 41.7 F., normal heptane melts at -130.5 F., while a mixture of these components in eutectic composition proportions melts at -l34.5 F. The eutectic composition is 93 per cent by weight benzene and 7 per cent by weight normal heptane.

Silica gel is the adsorbent used to adsorb selectively one of the components. This adsorbent, in general, adsorbs aromatic hydrocarbons in preference to other hydrocarbons. In a mixture of benzene and normal heptane, silica gel presents an adsorption isotherm of the type illustrated in Figure 3 of the drawing. However, on reference to Figure 3, if component A represents benzene and component B represents normal heptane, the curve crosses the horizontal line at a benzene concentration of 99 per cent (normal heptane 1 per cent). Thus, the composition of a benzene-normal heptane system at which silica gel becomes selective for the adsorption of normal heptane is 99 per cent benzene and vl per cent normal heptane.

Based upon each 100 pounds of feed stock containing 25 pounds normal heptane and 75 pounds benzene, the separation into benzene and heptane is made under the following conditions:

The feed stock is continuously introduced into the crystallizer tube through i'eed line 62. The liquid feed flows from right to left in the crystallizer tube il' and is chilled to a temperature of about 134 F. (just above the eutectic temperature, -l34.5 F.) at which temperature benzene crystallizes since it is the saturating component. The crystalline benzene is then moved by the screw 36 toward the heater 33. The liquid not frozen in Chiller 47 and which flows by displacement ii m right to left from chiller l toward heater il contains 12 per cent benzene and ist per cent normal heptane. Silica gel adsorbent, 35 pounds, enters the heater section 4| by way of adsorbent feed line l2. This adsorbent adsorbs most of the benzene, leaving a liquid of per cent benzene and 97.5 per cent normal heptane in the heater section di. This heater section is operated at a temperature of about 130 to 1317 F. or at such slightly lower temperature that normal heptane will not freeze out. Liquid of this composition, 2.5 per cent benzene-97 .5 per cent normal heptane, is removed from heater section il through pipe 50 and pumped 'through pipe 52 into the adiabatic section 58 at a point near the cooler d4. This liquid and the liquid already present at this point mix and the mixture contains 96 per cent normal heptane and l per cent benzene. Chiller 44 is operated at such a temperature that this mixture is chilled to very nearly the eutectic temperature (-l34.5 F.) at which temperature normal heptance crystallizes. The heptane crystals are moved by the screw IS toward the heater l 5. The heater i5 is operated'at a temperature of about -130 F. so that heptane crystals will just melt. Per 100 pounds of feed of the above-mentioned composition 25 pounds of a normal heptane product containing 24.925 pounds of normal heptane and 0.075 pound benzene are withdrawn through line i4. Some of the heptane melted by heater l5 flows toward the cooler to reflux the crystalline heptane.

The silica gel which is fed to the crystallizer through conduit l2 moves in the direction of the heater 33. As this gel with its charge of adsorbed benzene and the benzene crystals move through the adiabatic section 5l, they are reluxed by liquid benzene owing from right to left. This refiuxing operation increases the benzene content of the solids approaching the heater 33 until a point is reached near this heater when the concentration of benzene exceeds 99 per cent.

` At a concentration of 99 per cent benzene, the silica gel reverses itself and becomes an effective adsorbent for the normal heptane. The gel leaves the unit through conduit 3i with its charge of adsorbed heptane and occluded benzene.

The silica gel is regenerated by heating, with or without use of a stripping agent as needed. The adsorbate, free from moisture if steam is used for stripping, contains 9.84 per cent normal heptance and 90.36 per cent benzene and is returned with raw feed to the crystallizer. The adsorbent is recycled to the process.

The benzene crystals formed in the chiller 4'! are moved with the adsorbent through the adiabatic section 57 to the heater 33 in which they are melted. A portion of the melted benzene and desorbed benzene flows from right to left as a reluxing agent while the remainder, pounds containing 74.925 pounds benzene and 0.075 pound normal heptane, is removed through line 1l 32 as product. This product has a composition of benzene 99.9 per cent and normal heptane 0.10 per cent by weight.

If a normal heptance product of intermediate purity were desired, the liquid of 97.5 per cent normal heptane and 2.5 per cent benzene content withdrawn from heater 4l through line t@ and cycled to the adiabatic section 58 could be withdrawn as such a product.

For low temperature crystallization operations, the coolers 44 and 4l may be cooled by any desired and suitable means, as for example, propane, ethylene, or other hydrocarbon or non-hydrocarbon refrigerant. ln like manner, the heaters l5, 33, and 4l may be heated by any desired and suitable means. In the above given example, these heaters are called heaters since they are intended to maintain their immediate crystallizer sections at higher temperatures than the coolers or chillers. IThese higher temperatures may yet be far below atmospheric temperature, as in the benzene-normal heptane example given above. Such heaters may be operated by refrigerante as mentioned. For other separations, the coolers may need to be operated at atmospheric or even above atmospheric temperatures, while the heaters may need to be operated at higher than atmospheric temperatures. Under such conditions, Water as a heating or cooling agent, or steam or other heating or cooling media may be used.

The conduits 3l and 'ill2 may be such type of conveyors as are adapted for the transfer of solid material from one process point to another. For example, screw conveyors, bucket or belt conveyors or any other suitable type may be used.

For purposes of simplicity, many valves, pressure, and temperature recording and controlling apparatus and other auxiliary apparatus has not been shown. The installation and operation oi such auxiliary apparatus is understood by those skilled in the art.

The above description of my apparatus and of the use of this apparatus in separating a simple two-component system into its constitutent parts is given merely as illustrative of my apparatus and its use and my invention is not intended to be limited thereby, but only by the following claims.

Having described my invention, I claim:

1. A process for separating one hydrocarbon from a liquid mixture of said one hydrocarbon with another hydrocarbon, said one hydrocarbon being preferentially adsorbable from said mixture, said hydrocarbons being miscible in the liquid state and forming an eutectic mixture in the solid state, said mixture of hydrocarbons containing said one hydrocarbon in a concentration greater than its concentration in said eutectic mixture comprising, in combination, the steps of cooling said mixture to a temperature at which said one hydrocarbon crystallizes, but above that temperature at which said eutectic mixture crystallizes, contacting the resulting mixture of liquid and crystals with a solid adsorbent, said one hydrocarbon being preferentially adsorbed by said adsorbent and said adsorbent having an S-type adsorption curve, separating unadsorbed liquid from the adsorbent and crystals, heating the solid adsorbent with its charge of adsorbed one hydrocarbon and crystals of said one hydrocarbon to a temperature sufriciently high to melt the crystals and form a 4zone of nearly pure liquid one hydrocarbon passing a portion of the melted one hydrocarbon countercurrently and in contact with said solid adsorbent and crystals to reux same, removing the other portion of the melted one hydrocarbon as one product of the process, removing solid adsorbent containing adsorbed other hydrocarbon, desorbing said other hydrocarbon from the adsorbent and adding the desorbed material to the original feed stock, returning the desorbed adsorbent to the original contacting operation as the first mentioned solid adsorbent, chilling the separated unadsorbed liquid to a temperature at which said other hydrocarbon crystallizes, but above that temperature at which said eutectic mixture crystallizes, removing the crystals of said other hydrocarbon from the remaining liquid, passing this latter remaining liquid into the abovementioned solid adsorbent contacting operation, melting said crystals of said other hydrocarbon, reuxing the latter said crystals of said other hydrocarbon prior to said melting with a portion of the melted other hydrocarbon and removing the other portion of said melted other hydrocarbon as a second product of the process.

2. The lprocess of claim 1 wherein said one hydrocarbon is benzene and said other hydrocarbon is normal heptane, and the chilling and cooling operations are carried out at a temperature just above the eutectic temperature and the solid adsorbent is silica gel.

3. A process for separating one hydrocarbon from a liquid mixture of said one hydrocarbon with another hydrocarbon, said one hydrocarbn being preferentially adsorbable from said mixture, said hydrocarbons being miscible in the liquid state and forming a eutectic mixture in the solid state, said mixture of hydrocarbons containing said one hydrocarbon in a concentration greater than its concentration n said eutectic mixture comprising, in combination, the steps of introducing said mixture into an elongated and horizontally disposed cylindrical treating zone at a point about midway from a partition to one end, said partition being at about the center longitudinally of said zone, chilling said mixture to a temperature at which a portion of said one hydrocarbon crystallizes leaving a liquid of substantally eutectic composition, introducing a solid adsorbent having an S-type adsorption curve into said treating zone intermediate said partition and the point of introduction of said mixture, said one hydrocarbon being selectively adsorbed by said adsorbent from said liquid of eutectic composition, gradually transferring said adsorbent from its point of introduction and said crystals of said one hydrocarbon toward said one end of said zone, heating the mixture of crystals and adsorbent while in transit to a temperature above the melting temperature of said crystals and to form a zone of nearly pure one hydrocarbon adjacent said one end o said treating zone, passing a portion of the melted one hydrocarbon countercurrently with respect to the direction of travel of the mixture of the adsorbent and crystals to redux same, removing the remaining melted one hydrocarbon as one product of the process, removing solid adsorbent containing adsorbed other hydrocarbon from said one end of said cylindrical zone, desorbing the hydrocarbon from the removed adsorbent and returning the adsorbent to the treating zone as the iirst mentioned solid adsorbent, removing liquid rich in said other hydrocarbon from said treating zone at a point intermediate said partition and said one end and near said partition, introducing this withdrawn liquid into said treating zone at a point intermediate said partition and the other 13 end thereof, chilling this latter introduced mixture to a temperature at which a portion of said hydrocarbon countercurrently with respect to the direction of travel of said crystals of said other hydrocarbon 4. The process of claim 3 wherein said one hydrocarbon is benzene and said other hydrocarbon is normal heptane, and the chilling and cooling operations are carried out at a temperature just above the eutectic temperature and the solid adsorbent is silica gel.

References Cited in the le of this patent UNITED STATES PATENTS Number d Feb. 6. 1951 

1. A PROCESS FOR SEPARATING ONE HYDROCARBON FROM A LIQUID MIXTURE OF SAID ONE HYDROCARBON WITH ANOTHER HYDROCARBON, SAID ONE HYDROCARBON BEING PREFERENTIALLY ABSORBABLE FROM SAID MIXTURE, SAID HYDROCARBONS BEING MISCIBLE IN THE LIQUID STATE AND FORMING AN EUTECITIC MIXTURE IN THE SOLID STATE, SAID MIXTURE OF HYDROCARBONS CONTAINING SAID ONE HYDROCARBON IN A CONCENTRATION GREATER THAN ITS CONCENTRATION IN SAID EUTECTIC MIXTURE COMPRISING, IN COMBINATION, THE STEPS OF COOLING SAID MIXTURE TO A TEMPERATURE AT WHICH SAID ONE HYDROCARBON CRYSTALLIZES, BUT ABOVE THE TEMPERATURE AT WHICH SAID EUTECTIC MIXTURE CRYSTALLIZES, CONTACTING THE RESULTING MIXTURE OF LIQUID AND CRYSTALS WITH A SOLID ADSORBENT, SAID ONE HYDROCARBON BEING PREFERENTIALLY ADSORBED BY SAID ADSORBENT AND SAID ADSORBENT HAVING AN S-TYPE ADSORPTION CURVE, SEPARATING UNADSORBED LIQUID FROM THE ADSORBENT AND CRYSTALS, HEATING THE SOLID ADSORBENT WITH ITS CHARGE OF ADSORBED ONE HYDROCARBON AND CRYSTALS OF SAID ONE HYDROCARBON TO A TEMPERATURE SUFFICIENTLY HIGH TO MELT THE CRYSTALS AND FORM A ZONE OF NEARLY PURE LIQUID ONE HYDROCARBON PASSING A PROTION OF THE MELTED ONE HYDROCARBON COUNTERCURRENTLY AND IN CONTACT WITH SAID SOLID ADSORBENT AND CRYSTALS TO REFLUX SAME, REMOVING THE OTHER PORTION OF THE MELTED ONE HUDROCARBON AS ONE PRODUCT OF THE PROCESS, REMOVING SOLID ADSORBENT 